well, i had to abandon and use a different recipe because i was running out of time. but when i whisked it, it stayed the same consistency. i used a cup of unsweetened vanilla almond milk and 1 TBSP of apple cider vinegar

You can substitute a soured non-dairy milk for buttermilk. I've done it many a time; it is the almond milk that is the problem. I've had the best success with unsweetened soy milk and unsweetened rice milk. In turns of mimicking buttermilk, the soy curdles and has the taste, look, and thickness of cultured buttermilk. I know that almond milk has the best taste and probably the best health quotient--but I've found success with soy.